Please help with Java question about leaf and subtrees. Please help with TODO

// If not a leaf node, we will need to insert in one of our subtrees. else { if (n.nodeType == 2) { if (item < n.items[0]) { Node result = put(n.subtrees[0], item); // if the resulting root is not a 4-node, we can insert it as our new left. if (result.nodeType != 4) { n.subtrees[0] = result; } // otherwise, we need to fix it by splitting it else { Node newLeft = new Node(result.items[0], result.subtrees[0], result.subtrees[1]); Node newMiddle = new Node(result.items[2], result.subtrees[2], result.subtrees[3]); n.items[1] = n.items[0]; n.items[0] = result.items[1]; n.subtrees[2] = n.subtrees[1]; n.subtrees[1] = newMiddle; n.subtrees[0] = newLeft; n.nodeType = 3; } } else { Node result = put(n.subtrees[1], item); // if the resulting root is not a 4-node, we can insert it as our new right. if (result.nodeType != 4) { n.subtrees[1] = result; } // otherwise, we need to fix it by splitting it else { Node newMiddle = new Node(result.items[0], result.subtrees[0], result.subtrees[1]); Node newRight = new Node(result.items[2], result.subtrees[2], result.subtrees[3]); n.items[1] = result.items[1]; n.subtrees[2] = newRight; n.subtrees[1] = newMiddle; n.nodeType = 3; } } return n;

} else if (n.nodeType == 3) { // TODO

throw new RuntimeException("Implement me!"); } else throw new RuntimeException("ERROR: " + n.nodeType + "-node found while inserting");